Impact resistant, flame retardant thermoplastic molding composition

ABSTRACT

A thermoplastic molding composition characterized by its flame retardance and impact strength is disclosed. The composition contains (A) linear aromatic (co)polycarbonate, (B) a graft (co)polymer having core-shell morphology, the shell containing polymerized alkyl(meth)acrylate and the core containing interpenetrated and inseparable polyorganosiloxane and poly(meth)alkyl acrylate components, (C) a phosphorous-containing flame retardant compound, (D) fluorinated polyolefin and (E) a boron compound, and optionally SAN. The composition is further characterized in that it contains no polyalkylene terephthalate.

FIELD OF THE INVENTION

The invention relates to thermoplastic molding compositions and inparticular to impact-modified, flame retardant thermoplastic moldingcompositions that contain aromatic polycarbonate resin.

TECHNICAL BACKGROUND OF THE INVENTION

Impact-modified blends of polycarbonate are known. Also known are flameresistant polycarbonate compositions where the flame retarding agent ishalogen-free.

The relevant art is noted to include JP 2001 031 860 that disclosed animpact strength composition, said to be hydrolytically stable andchemically resistant, containing polycarbonate, a graft elastomer havinga core-shell structure and red phosphorus.

An impact modified thermoplastic molding composition containingpolycarbonate and a graft (co)polymer wherein the graft base includes arubber selected from a group that includes silicone-acrylate compositehas been disclosed in U.S. Pat. No. 7,067,567. The graft (co)polymer isexemplified by methyl methacrylate-grafted silicone-butyl acrylatecomposite rubber. An impact resistance composition containingpolycarbonate and graft polymer based on a silicone-butyl acrylatecomposite rubber is disclosed in U.S. Pat. No. 4,888,388.

A flame retardant, chemically resistant and thermally stable compositioncontaining a halogenated aromatic polycarbonate resin, aromaticpolyester resin, and graft rubber polymer composite is disclosed in JP04 345 657. The graft rubber is said to be obtained by grafting vinylmonomer(s) onto rubber particles consisting of a poly-organosiloxanerubber and a polyalkyl (meth)acrylate rubber entangled so as not to beseparated from each other.

JP8259791 is considered to disclose a flame-retardant resin compositionsaid to feature excellent impact resistance and flame retardance andcontaining polycarbonate resin with a phosphoric ester compound and aspecific composite-rubber-based graft copolymer. Thecomposite-rubber-based graft copolymer is obtained by grafting at leastone vinyl monomer (e.g. methyl methacrylate) onto a composite rubberthat contains 30-99% polyorganosiloxane component and 70-1% of polyalkyl (meth)acrylate rubber component.

JP 7316409 disclosed a composition having good impact resistance andflame retardance containing polycarbonate, phosphoric ester and aspecified graft copolymer based on a composite rubber. The graftcopolymer is obtained by graft polymerization of one or more vinylmonomers onto a composite rubber in which polyorganosiloxane componentand polyalkyl (meth)acrylate rubber component are entangled together soas not to be separable.

U.S. Pat. No. 4,824,723 disclosed a flame retardant material thatcontains polycarbonate and a flame retardant. Phosphorous compoundsalone or in combination with zinc salt is referred to among thedisclosed flame retardants.

U.S. Pat. No. 4,963,619 disclosed a thermoplastic polycarbonate moldingcomposition containing polycarbonates, siloxane-containing graftpolymers and, optionally, other thermoplasts and/or standard additives.The composition is said to feature high toughness, particularly at lowtemperatures.

U.S. Pat. No 6,423,766 disclosed a flame-retardant polycarbonate resincomposition, containing polycarbonate resin, a composite rubbery graftcopolymer, a halogen-free phosphoric ester and polytetrafluoroethylene.The composition is said to exhibit improved mechanical properties,moldability, flowability, and flame retardance. The graft rubber isbased on polyorganosiloxane rubber component and polyalkyl acrylaterubber component and the two components are inter-twisted andinseparable from each other. The grafted rubber is grafted with one ormore vinyl monomers.

A flame retardant resin composition containing polycarbonates, ahalogenated flame-retardant, and a rubber-occluded flame retardantsynergist has been disclosed in U.S. Pat. No. 4,339,556. Zinc borate isdisclosed among the suitable flame retardant synergists.

A flame retardant polycarbonate composition exhibiting reduced heatrelease rate has been disclosed in U.S. Pat. No. 5,153,251. Thecomposition contains a blend of polydiorganosiloxane fluid and calcinedclay. Zinc borate is disclosed as an additive to impart improved flamedrip properties. U.S. Pat. No. 5,266,618 disclosed a flame-retardantresin composition that contains polycarbonate resin, an optional graftpolymer, a phosphorus compound, a boron compound, andpolyorganosiloxane. A thermoplastic molding composition that containspolycarbonate, vinyl copolymer, graft polymer, and a finely dividedcompound selected from the group consisting of zinc sulfide, zincphosphate, zinc borate and zinc sulfate is disclosed in U.S. Pat. No.6,596,800 to exhibit improved mechanical properties.

Currently pending patent application Ser. No. 11/713,352, filed Mar. 2,2007 assigned to the present assignee disclosed compositions containingpresently relevant components.

SUMMARY OF THE INVENTION

A thermoplastic molding composition characterized by its flameretardance and impact strength is disclosed. The composition contains(A) linear aromatic (co)polycarbonate, (B) a graft (co)polymer havingcore-shell morphology, the shell containing polymerizedalkyl(meth)acrylate and the core containing interpenetrated andinseparable polyorganosiloxane and poly(meth)alkyl acrylate components,(C) a phosphorous-containing flame retardant compound, (D) fluorinatedpolyolefin and (E) a boron compound. The composition is furthercharacterized in that it contains no polyalkylene terephthalate.

DETAILED DESCRIPTION OF THE INVENTION

The inventive composition that features exceptional flame retardance andimpact strength contains

-   A) 50 to 95 percent by weight (pbw), preferably 65 to 90 pbw, most    preferably 70 to 85 pbw of linear aromatic (co)polycarbonate having    a weight-average molecular weight of at least 25,000 preferably at    least 26,000 g/mol.,-   B) 1 to 15 preferably 3 to 12, more preferably 5 to 8 pbw of a graft    (co)polymer having a core-shell morphology, comprising a grafted    shell that contains polymerized alkyl(meth)acrylate and a composite    rubber core that contains interpenetrated and inseparable    polyorganosiloxane and poly(meth)alkyl acrylate components, where    the weight ratio of polyorganosiloxane to poly(meth)alkylacrylate to    rigid shell is 70-90/5-15/5-15, and-   C) 2 to 20, preferably 5 to 15, particularly preferably 7 to 15,    most preferably 10 to 13 pbw of a phosphorus-containing compound,    preferably organic phosphoric or phosphonic acid ester, and-   D) 0.1 to 2, preferably 0.2 to 1, most preferably 0.2 to 0.5 pbw of    fluorinated polyolefin, and-   E) 0.1 to 15, preferably 1 to 10, most preferably 1 to 5 pbw of a    boron compound, preferably zinc borate, the percents, all    occurrences being relative to the weight of the composition, with    the proviso that polyalkylene terephthalate is not included.

Any numerical range recited herein is intended to include all sub-rangessubsumed therein.

Component A

Suitable linear aromatic (co)polycarbonates (including linear aromaticpolyestercarbonates) are known. Such (co)polycarbonates may be preparedby known processes (see for instance Schnell's “Chemistry and Physics ofPolycarbonates”, Interscience Publishers, 1964) and are widely availablein commerce, for instance Makrolon® polycarbonate a product of BayerMaterialScience.

Aromatic polycarbonates may be prepared by the known melt process or thephase boundary process.

Aromatic dihydroxy compounds suitable for the preparation of aromaticpolycarbonates and/or aromatic polyester carbonates conform to formula(I)

wherein

-   A represents a single bond, C₁- to C₅-alkylene, C₂- to    C₅-alkylidene, C₅- to C₆-cycloalkylidene, —O—, —SO—, —CO—, —S—,    —SO₂—, C₆- to C₁₂-arylene, to which there may be condensed other    aromatic rings optionally containing hetero atoms, or a radical    conforming to formula (II) or (III)

The substituents B independently one of the others denote C₁- toC₁₂-alkyl, preferably methyl,

-   x independently one of the others denote 0, 1 or 2,-   p represents 1 or 0, and-   R⁵ and R⁶ are selected individually for each X¹ and each    independently of the other denote hydrogen or C₁- to C₆-alkyl,    preferably hydrogen, methyl or ethyl,-   X¹ represents carbon, and m represents an integer of 4 to 7,    preferably 4 or 5, with the proviso that on at least one atom X¹, R⁵    and R⁶ are both alkyl groups.

Preferred aromatic dihydroxy compounds are hydroquinone, resorcinol,dihydroxydiphenols, bis-(hydroxyphenyl)-C₁-C₅-alkanes,bis-(hydroxyphenyl)-C₅-C₆-cycloalkanes, bis-(hydroxyphenyl) ethers,bis-(hydroxyphenyl) sulfoxides, bis-(hydroxyphenyl) ketones,bis-(hydroxyphenyl)-sulfones andα,α-bis-(hydroxyphenyl)-diisopropyl-benzenes. Particularly preferredaromatic dihydroxy compounds are 4,4′-dihydroxydiphenyl, bisphenol A,2,4-bis-(4-hydroxyphenyl)-2-methylbutane,1,1-bis-(4-hydroxyphenyl)-cyclohexane,1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane,4,4′-dihydroxydiphenyl sulfide, 4,4′-dihydroxydiphenyl-sulfone. Specialpreference is given to 2,2-bis-(4-hydroxphenyl)-propane (bisphenol A).These compounds may be used individually or in the form of any desiredmixtures.

Chain terminators suitable for the preparation of thermoplastic aromaticpolycarbonates include phenol, p-chlorophenol, p-tert.-butylphenol, aswell as long-chained alkylphenols, such as4-(1,3-tetra-methylbutyl)-phenol or monoalkylphenols or dialkylphenolshaving a total of from 8 to 20 carbon atoms in the alkyl substituents,such as 3,5-di-tert.-butylphenol, p-isooctylphenol, p-tert.-octylphenol,p-dodecylphenol and 2-(3,5-dimethylheptyl)-phenol and4-(3,5-dimethylheptyl)-phenol. The amount of chain terminators to beused is generally 0.5 to 10% based on the total molar amount of thearomatic dihydroxy compounds used. The suitable linear(co)polycarbonates include polyestercarbonates, including such as aredisclosed in U.S. Pat. Nos. 4,334,053; 6,566,428 and in CA 1173998, allincorporated herein by reference. Aromatic dicarboxylic acid dihalidesfor the preparation of the suitable aromatic polyestercarbonates includediacid dichlorides of isophthalic acid, terephthalic acid, diphenylether 4,4′-dicarboxylic acid and naphthalene-2,6-dicarboxylic acid.Particularly preferred are mixtures of diacid dichlorides of isophthalicacid and terephthalic acid in a ratio of from 1:20 to 20:1.

The content of carbonate structural units in the thermoplastic aromaticpolyestercarbonates is preferably up to 100 mol. %, especially up to 80mol. %, particularly preferably up to 50 mol. %, based on the sum ofester groups and carbonate groups. Both the esters and the carbonatescontained in the aromatic polyester carbonates may be present in thepolycondensation product in the form of blocks or in a randomlydistributed manner.

The thermoplastic linear aromatic poly(ester) carbonates haveweight-average molecular weights (measured by gel permeationchromatography) of at least 25,000, preferably at least 26,000. Thethermoplastic aromatic poly(ester) carbonates may be used alone or inany desired mixture.

The amount of component A in the inventive composition is 53 to 96.8percent by weight (pbw), advantageously 65 to 90.8, most preferably 73.5to 83.8 pbw relative to the weight of the composition.

Component B

Component B is at least one graft polymer of

-   B.1 from 5 to 95 wt. %, preferably from 10 to 90 wt. %, of one or    more vinyl monomers on-   B.2 from 95 to 5 wt. %, preferably from 90 to 10 wt. %, of one or    more graft bases selected from the group of the silicone rubbers    (B.2.1) and silicone acrylate rubbers (B.2.2).

The graft copolymer B may be prepared by free-radical polymerization,for example by emulsion, suspension, solution or mass polymerization,preferably by emulsion or mass polymerization.

Suitable monomers B.1 include vinyl monomers such as vinyl aromaticcompounds and/or ring-substituted vinyl aromatic compounds (e.g.styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene), methacrylicacid (C₁-C₈)-alkyl esters (e.g. methyl methacrylate, ethyl methacrylate,2-ethylhexyl methacrylate, allyl methacrylate), acrylic acid(C₁-C₈)-alkyl esters (e.g. methyl acrylate, ethyl acrylate, n-butylacrylate, tert-butyl acrylate), organic acids (e.g. acrylic acid,methacrylic acid) and/or vinyl cyanides (e.g. acrylonitrile andmethacrylonitrile) and/or derivatives (e.g. anhydrides and imides) ofunsaturated carboxylic acids (e.g. maleic anhydride andN-phenyl-maleimide). These vinyl monomers may be used alone or asmixtures of at least two monomers.

The preferred monomers of B.1 are styrene, α-methylstyrene, methylmethacrylate, n-butyl acrylate and acrylonitrile. Particularly preferredmonomer B.1 is methyl methacrylate as the monomer.

The glass transition temperature of the graft base B.2 is lower than 10°C., preferably lower than 0° C., particularly preferably lower than −20°C. The graft base B.2 has a median particle size (d₅₀ value) of from0.05 to 10 μm, preferably from 0.06 to 5 μm, particularly preferablyfrom 0.08 to 1 μm. The diameter which differentiates between two equalparts by weight of a given sample of particulate matter, one partcontaining all particles larger than that diameter and the other partcontaining all grains smaller is the median diameter. It can bedetermined by means of ultracentrifuge measurement (W. Scholtan, H.Lange, Kolloid, Z. und Z. Polymere 250 (1972), 782-1796).

Suitable silicone rubbers according to B.2.1 are silicone rubbers havinggraft-active sites, the preparation method of which is described, forexample, in U.S. Pat. No. 2,891,920, U.S. Pat. No. 3,294,725, DE-OS 3631 540, EP 249964, EP 430134 and U.S. Pat. No. 4,888,388, allincorporated herein by reference. It is preferably prepared by emulsionpolymerization, in which siloxane monomeric structural units,crosslinking or branching agents and optionally grafting agents areused.

Suitable siloxane monomeric structural units include dimethylsiloxane orcyclic organosiloxanes having at least 3 ring members, preferably from 3to 6 ring members, for example hexamethylcyclotrisiloxane,octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane,dodecamethylcyclohexasiloxane, trimethyl-triphenyl-cyclotrisiloxane,tetramethyl-tetraphenyl-cyclotetrasiloxane,octaphenylcyclotetrasiloxane. These organosiloxane monomers may be usedalone or as mixtures of two or more monomers. The silicone rubberpreferably contains not less than 50 wt. % and particularly preferablynot less than 60 wt. % organosiloxane, based on the total weight of thesilicone rubber component.

Examples of crosslinking or branching agents include silane-basedcrosslinking agents having a functionality of 3 or 4, particularlypreferably 4. Preferred agents include trimethoxymethylsilane,triethoxyphenylsilane, tetramethoxysilane, tetraethoxysilane,tetra-n-propoxysilane and tetrabutoxysilane. Crosslinking agent may beused alone or in a mixture of two or more crosslinking agents.Tetraethoxysilane is particularly preferred.

The crosslinking agent may be used in an amount of 0.1 to 40 wt. %,based on the total weight of the silicone rubber component. The amountof crosslinking agent is selected so that the degree of swelling of thesilicone rubber, measured in toluene, is from 3 to 30, preferably from 3to 25 and particularly preferably from 3 to 15. The degree of swellingis defined as the weight ratio of the amount of toluene absorbed by thesilicone rubber when it is saturated with toluene at 25° C., and theamount of silicone rubber in the dry state. The determination of thedegree of swelling is described in detail in U.S. Pat. No. 4,877,831,incorporated herein by reference.

Suitable grafting agents are compounds that are capable of formingstructures having the following formulae:CH₂═C(R²)—COO—(CH₂)_(p)—SiR¹ _(n)O_((3-n)/2)  (V-1)CH₂═CH—SiR¹ _(n)O_((3-n)/2)  (V-2) orHS—(CH₂)_(p)—SiR¹ _(n)O_((3-n)/2)  (V-3),wherein

-   R¹ is C₁-C₄-alkyl, preferably methyl, ethyl or propyl, or phenyl,-   R² is hydrogen or methyl,-   n is 0, 1 or 2 and-   p is 1 to 6.

Preferred examples include:β-methacryloyloxy-ethyidimethoxymethyl-silane,γ-methacryloyloxy-propylmethoxydimethyl-silane,γ-methacryloyloxy-propyldimethoxymethyl-silane,γ-methacryloyloxy-propyltrimethoxy-silane,γ-methacryloyloxy-propylethoxydiethyl-silane,γ-methacryloyloxy-propyldiethoxymethyl-silane,δ-methacryloyl-oxy-butyldiethoxymethyl-silane or mixtures thereof. From0 to 20 wt. % of grafting agent may be used, based on the total weightof the silicone rubber.

The silicone rubber may be prepared by emulsion polymerization, asdescribed, for example, in U.S. Pat. Nos. 2,891,920 and 3,294,725. Thesilicone rubber is thereby obtained in the form of aqueous latex. Tothat end, a mixture containing organosiloxane, crosslinking agent andoptionally grafting agent is mixed with water, under shear, for exampleby means of a homogenizer, in the presence of an emulsifier based onsulfonic acid, such as, for example, alkylbenzenesulfonic acid oralkylsulfonic acid, the mixture polymerizing completely to form thesilicone rubber latex. An alkylbenzenesulfonic acid is particularlysuitable because it acts not only as emulsifier but also aspolymerization initiator. In this case, a combination of the sulfonicacid with a metal salt of an alkylbenzenesulfonic acid or with a metalsalt of an alkylsulfonic acid is advantageous because the polymer isstabilized thereby during the subsequent graft polymerization.

After the polymerization, the reaction is terminated by neutralizing thereaction mixture by addition of an aqueous alkaline solution, forexample by addition of an aqueous sodium hydroxide, potassium hydroxideor sodium carbonate solution.

Silicone acrylate rubbers (B.2.2) are also suitable as graft bases B.2.These rubbers are composite rubbers having graft-active sites andcontaining from 10 to 90 wt. % silicone rubber component and from 90 to10 wt. % polyalkyl (meth)acrylate rubber component, the two mentionedrubber components in the composite rubber interpenetrating so that theycannot substantially be separated from one another.

Silicone acrylate rubbers are known and are described, for example, inU.S. Pat. Nos. 5,807,914, and 4,888,388, both incorporated herein byreference.

Suitable silicone rubber components therefor are those as alreadydescribed under B.2.1.

Suitable polyalkyl (meth)acrylate rubber components of the siliconeacrylate rubbers according to B.2.2 may be prepared from methacrylicacid alkyl esters and/or acrylic acid alkyl esters, a crosslinking agentand a grafting agent. Examples of preferred methacrylic acid alkylesters and/or acrylic acid alkyl esters are C₁- to C₈-alkyl esters, forexample methyl, ethyl, n-butyl, tert-butyl, n-propyl, n-hexyl, n-octyl,n-lauryl and 2-ethylhexyl esters; haloalkyl esters, preferablyhalo-C₁-C₈-alkyl esters, such as chloroethyl acrylate, as well asmixtures of these monomers. n-Butyl acrylate is particularly preferred.

As crosslinking agents for the polyalkyl (meth)acrylate rubber componentof the silicone acrylate rubber there may be used monomers having morethan one polymerizable double bond. Preferred examples of crosslinkingmonomers are esters of unsaturated monocarboxylic acids having from 3 to8 carbon atoms and unsaturated monohydric alcohols having from 3 to 12carbon atoms, or saturated polyols having from 2 to 4 OH groups and from2 to 20 carbon atoms, such as ethylene glycol dimethacrylate, propyleneglycol dimethacrylate, 1,3-butylene glycol dimethacrylate and1,4-butylene glycol dimethacrylate. The crosslinking agents can be usedalone or in mixtures of at least two crosslinking agents.

Examples of preferred grafting agents include allyl methacrylate,triallyl cyanurate, triallyl isocyanurate or mixtures thereof. Allylmethacrylate may also be used as crosslinking agent. The grafting agentsmay be used alone or in mixtures of at least two grafting agents.

The amount of crosslinking agent and grafting agent is from 0.1 to 20wt. %, based on the total weight of the polyalkyl (meth)acrylate rubbercomponent of the silicone acrylate rubber.

The silicone acrylate rubber may be produced by first preparing thesilicone rubber (B.2.1) as aqueous latex. The latex may subsequently beenriched with the methacrylic acid alkyl esters and/or acrylic acidalkyl esters, the crosslinking agent and the grafting agent, andpolymerization is carried out. Preference is given to emulsionpolymerization initiated by free radicals, for example by a peroxide,azo or redox initiator. Particular preference is given to the use of aredox initiator system, in particular a sulfoxylate initiator systemprepared by combining iron sulfate, disodium ethylenediaminetetraacetate, rongalite and hydroperoxide.

The grafting agent used in the preparation of the silicone rubber hasthe effect that the polyalkyl (meth)acrylate rubber component is bondedcovalently to the silicone rubber component. In the polymerisation, thetwo rubber components interpenetrate and thus form the composite rubber,which after the polymerization can no longer be separated into itsconstituents of silicone rubber component and polyalkyl (meth)acrylaterubber component.

For the preparation of the silicone (acrylate) graft rubbers themonomers B.1 are grafted onto the rubber base B.2.

The polymerization methods are described, for example, in U.S. Pat. Nos.4,877,831 and 4,888,388 and EP 430134, incorporated herein by reference.

The graft polymerization may be carried out, for example, according tothe following polymerization method: In a single- or multi-step emulsionpolymerization initiated by free radicals, the desired vinyl monomersB.1 are polymerized onto the graft base, which is in the form of aqueouslatex. The grafting efficiency should be as high as possible and ispreferably greater than or equal to 10%. The grafting efficiency issubstantially dependent on the grafting agent or used. Afterpolymerization to the silicone (acrylate) graft rubber, the aqueouslatex is added to hot water in which metal salts have previously beendissolved, such as, for example, calcium chloride or magnesium sulfate.The silicone (acrylate) graft rubber thereby coagulates and may then beseparated off.

The methacrylic acid alkyl ester and acrylic acid alkyl ester graftrubbers mentioned as component B) are commercially available, forexample Metablen® SX 005 a product of Mitsubishi Rayon Co. Ltd.

The preferred graft (co)polymer suitable in the context of the inventionhas core/shell morphology. It may be obtained by graft polymerizingalkyl(meth)acrylate and optionally a copolymerizable vinyl monomer ontoa composite rubber core. The composite rubber core that includesinterpenetrated and inseparable network (IPN) polyorganosiloxane andpoly(meth)alkyl acrylate components is characterized in that its glasstransition temperature is below 0° C., preferably below −20° C.,especially below −40° C.

The preferred core is polysiloxane-alkyl(meth)acrylate interpenetratingnetwork (IPN) type polymer that contains polysiloxane and butylacrylate.The shell is a rigid phase, preferably polymerized ofmethylmethacrylate. The weight ratio ofpolysiloxane/alkyl(meth)acrylate/rigid shell is 70-90/5-15/5-15,preferably 75-85/7-12/7-12, most preferably 80/10/10.

Component C

Phosphorus-containing compounds suitable in the context of the inventioninclude oligomeric organic phosphoric or phosphonic acid estersconforming structurally to formula (IV)

wherein

-   R¹, R², R³ and R⁴ independently one of the others, each represents    C₁- to C₈-alkyl, or C₅-₆-cycloalkyl, C₆-₂₀-aryl or C₇-₁₂-aralkyl    each optionally substituted by alkyl, preferably by C₁-₄-alkyl,-   n independently one of the others denotes 0 or 1, preferably 1,-   q denotes 0.5 to 30, preferably 0.8 to 15, particularly preferably 1    to 5, especially 1 to 2, and-   X is a mono- or poly-nuclear aromatic radical having from 6 to 30    carbon atoms, or an aliphatic radical having from 2 to 30 carbon    atoms, which may be OH-substituted and may contain up to 8 ether    bonds. The aliphatic radical may be linear or branched.

Preferably, R¹, R², R³ and R⁴ each independently of the othersrepresents C₁-₄-alkyl, phenyl, naphthyl or phenyl-C₁-₄-alkyl. In theembodiments where any of R¹, R², R³ and R⁴ is aromatic, it may besubstituted by alkyl groups, preferably by C₁-₄-alkyl. Particularlypreferred aryl radicals are cresyl, phenyl, xylenyl, propylphenyl orbutylphenyl.

In the preferred embodiment X represents a mono- or poly-nucleararomatic radical having from 6 to 30 carbon atoms. It is preferablyderived from any of the aromatic dihydroxy compounds of formula (I).

-   X particularly preferably represents at least one member selected    from the group consisting of

Especially, X may be derived from resorcinol, hydroquinone, bisphenol Aor diphenylphenol and particularly preferably from bisphenol A.

Further suitable phosphorus-containing compounds are compounds offormula (IVa)

wherein

-   R¹, R², R³, R⁴, n and q are as defined for formula (IV),-   m independently one of the others represents 0, 1, 2, 3 or 4,-   R⁵ and R⁶ independently one of the others represents C₁-₄-alkyl,    preferably methyl or ethyl, and-   Y represents C₁- to C₇-alkylidene, C₁-₇-alkylene,    C₅-₁₂-cycloalkylene, C₅-₁₂-cycloalkylidene, —O—, —S—, —SO₂ or —CO—,    preferably isopropylidene or methylene.    Particularly preferred is

wherein q is 1 to 2.

Such phosphorus compounds are known (see, for example, U.S. Pat. Nos.5,204,394 and 5,672,645, both incorporated herein by reference) or maybe prepared by known methods (e.g. Ullmanns Enzyklopädie der technischenChemie, Vol. 18, p. 301 et seq. 1979; Houben-Weyl, Methoden derOrganischen Chemie, Vol. 12/1, p. 43; Beilstein Vol. 6, p. 177).

The phosphorous-containing compound is present in the inventivecomposition in an amount of 2 to 20, preferably 5 to 15, particularlypreferably 7 to 15, most preferably 10 to 13 percent relative to theweight of the composition.

Component D

Fluorinated polyolefins are known and are described, for example, inU.S. Pat. No. 5,672,645 incorporated herein by reference. They aremarketed, for example, under the trademark Teflon®30N by DuPont.

The fluorinated polyolefins may be used in the pure form or in the formof a coagulated mixture of emulsions of the fluorinated polyolefins withemulsions of the graft polymers (component B) or with an emulsion of acopolymer, preferably based on styrene/acrylonitrile, the fluorinatedpolyolefin being mixed as an emulsion with an emulsion of the graftpolymer or of the copolymer and the mixture then being coagulated. Thefluorinated polyolefins may be mixed as powders with a powder orgranules of the graft polymer or copolymer and the mixture thencompounded in the melt in conventional units, such as internal kneaders,extruders or twin-screw extruders.

The fluorinated polyolefins may also be used in the form of a masterbatch, which is prepared by emulsion polymerization of at least one monoethylenically unsaturated monomer in the presence of an aqueousdispersion of the fluorinated polyolefin. Preferred monomer componentsare styrene, acrylonitrile and mixtures thereof. The polymer is employedas a free-flowing powder, after acidic precipitation and subsequentdrying.

The coagulates, pre-compounds or master batches conventionally havesolids contents of fluorinated polyolefin of 5 to 95 wt. %, preferably 7to 60 wt. %.

Component D may be contained in the composition according to theinvention in an amount of preferably 0.1 to 2, preferably 0.2 to 1 andmost preferably 0.2 to 0.5 percent relative to the total weight of thecomposition.

Component E

Component E is an inorganic boron compound with elements of the 6th MainGroup of the Periodic Table, preferably with oxygen. Preferredoxygen-containing boron compounds are metal salts of the borates, inwhich case the oxygen-containing boron compound may be present asorthoborate, metaborate, hydroxoborate or polyborate. Examples includeboric acid, boron oxide and borates. The borates include zinc boratessuch as zinc tetraborate, zinc metaborate and basic zinc borate, bariumborates such as barium orthoborate, barium metaborate, barium diborateand barium tetraborate, lead borate, cadmium borate and magnesiumborate. Metals of the 1st to 5th Main Groups or of the 1st to 8thSubgroups of the Periodic Table, preferably metals of the 1st and 2ndMain Groups or of the 1st and 2nd Subgroups of the Periodic Table, actas counter ions of the borates; preferred are Li₃[BO₃], Li[BO₂],Li[B(OH)₄], Na₃[B₃O₆], Na₂B₄O₇.4 H₂O, Na₂B₄O₇.10H₂O, NaCaB₅O₉.6H₂O,K₃[B₃O₆], KB₅O₈.4H₂O, Mg₃[BO₃]₂, Ca[BO₃]₂, Ca[BO₂]₂, CaB₄O₇.4H₂O,Ca₂B₆O₁₁.5H₂O, Ca₂B₆O₁₁.7H₂O, Ca₄B₁₀O₁₉.7H₂O, Ca₅B₁₂O₂₃.9H₂O, Sr[BO₂]₂,Ba₃[B₃O₆]₂, Cu₃[BO₃]₂, Zn₃[BO₃]₂, Zn₂B₆O₁₁, Zn₄B₂O₇.H₂O, Zn₂B₆O₁₁.3.5H₂Oand ZnB₄O₇.4H₂O. Other suitable zinc borate hydrate include Zn₄B₂O₇.H₂O,Zn₂B₆O₁₁.3.5H₂O and ZnB₄O₇.4H₂O.

The boron compounds may be used singly or as mixtures.

The preferred boron compound is Zinc borate. The preferred zinc borateconforms to mZnO.nB2O3.xH2O where the ratio of x/m/n is around0-7/1-5/2-6. The preferred zinc borate is well known and commerciallyavailable.

The median particle diameter (d₅₀) of the boron compound is 1 nm to 20μm, preferably 0.1 μm to 15 μm, and particularly preferably 0.5 μm-12μm.

Other Components

The inventive composition may include an optional styrenic copolymer,preferably styrene-acrylonitrile (SAN) at an amount of up to 50,preferably 10 to 30 pbw. The inventive composition may further includeeffective amounts of any of the additives known for their function inthe context of thermoplastic polycarbonate molding compositions. Theseinclude any one or more of lubricants, mold release agents, for examplepentaerythritol tetrastearate, nucleating agents, antistatic agents,thermal stabilizers, light stabilizers, hydrolytic stabilizers, fillersand reinforcing agents, colorants or pigments, as well as further flameretarding agents, other drip suppressants or a flame retardingsynergists.

The inventive composition may be produced by conventional proceduresusing conventional equipment. It may be used to produce moldings of anykind by thermoplastic processes such as injection molding, extrusion andblow molding methods. The Examples which follow are illustrative of theinvention.

EXAMPLES

In the preparation of exemplified compositions, the components andadditives were melt compounded in a twin screw extruder ZSK 30 at atemperature profile from 200° C. to 300° C. The pellets obtained weredried in a forced air convection oven at 90° C. for 4 to 6 hours. Theparts were injection molded at temperatures equal to or higher than 240°C. and mold temperature of about 75° C.

In preparing the compositions described below the following componentswere used:

-   Polycarbonate: a bisphenol-A based linear homopolycarbonate having    melt flow rate of about 4 g/10 min (at 300° C., 1.2 kg) per ASTM D    1238(Makrolon 3108, a product of Bayer Material Science LLC)-   Graft (co)polymer: methyl methacrylate (MMA) shell—grafted on to a    core of siloxane(Si)-butyl acrylate (BA)composite rubber. The weight    ratio of Si/BA/MMA is 80/10/10.-   Phosphorous compound (designated P-compound): conforming to

All exemplified compositions contained 0.4 phr fluorinated polyolefin(PTFE) introduced in the form of SAN-encapsulated PTFE in free-flowingpowder form, containing 50 pbw PTFE (designated in the table asPTFE-SAN).

The boron compound used in the exemplified compositions (designated inthe table as B-compound) was zinc borate in powder form having medianparticle size of 2 to 10 microns.

Each of the exemplified compositions further included the followingconventional additives: about 0.1 wt. % thermal stabilizer, 0.4 wt. %lubricant and 0.5 wt. % aluminium oxide hydroxide. These additives arebelieved to have no criticality in the context of the inventivecomposition.

The melt flow rates (MFR) of the compositions were determined inaccordance with ASTM D-1238 at 240° C., 5 Kg load.

The notched impact strength (NI) was determined at room temperature(about 23° C.) in accordance with ASTM D-256 using specimens ⅛″ inthickness. Failure mode was determined by observation; accordingly “D”means ductile failure and D/B means ductile/brittle failure.

Instrumental Impact strength was determined at room temperature inaccordance with ASTM D3763 using specimens ⅛″.

The flammability rating was determined according to UL-94 on specimens1.5 mm thick and 0.75 mm thick. Flammability rating in accordance withUL94 5V protocol has also been performed on plaques measuring 6″×6″×2.3mm thick.

TABLE 1 Example 1 2 3 (com.) 4 (com.) Component A: 78.5 78.2 78.0 80.7Polycarbonate, wt. % Component B: 5.75 6.0 6.25 7 Graft copolymer, wt. %Component C: 12.5 12.5 12.5 8.5 P-compound, wt. % Component D: 0.8 0.80.8 0.8 PTFE-SAN Component E: 1.48 1.48 1.48 2.0 B-compound, wt %Properties MFR, g/10 min 11.1 10.5 10.9 2.0 Impact Strength, 10.0 11.211.4 13.8 notched Izod@23° C., ⅛″, ft-lb/in Instrumental Impact36.5/D^((a)) 37.9/D^((a)) 38.9/D^((a) 22.4 strength, ⅛″ @ room DB^((a))temperature, Energy @total, ft · lb Flammability, UL94 @ V-0 V-0 V-0Failed 1.5 mm Flammability, UL 5A 5A 5B 5A 5 V @ 2.3 mm ^((a))D -indicates ductile break; DB - indicates ductile-brittle break

Examples 1 and 2 that represent the invention show a combination ofexceptional flame resistance and impact performance. Examples 3 and 4are comparative examples exhibiting inferior properties that point tothe criticality of the claimed relative amounts of the components.

Although the invention has been described in detail in the foregoing forthe purpose of illustration, it is to be understood that such detail issolely for that purpose and that variations can be made therein by thoseskilled in the art without departing from the spirit and scope of theinvention except as it may be limited by the claims.

1. A thermoplastic molding composition comprising A) 50 to 95 percentlinear aromatic (co)polycarbonate B) 1 to 15 percent graft (co)polymerhaving a core-shell morphology, including a grafted shell that consistsof polymerized alkyl(meth)acrylate and a composite rubber core thatcontains interpenetrated and inseparable polyorganosiloxane andpoly(meth)alkylacrylate components, wherein the weight ratio ofpolyorganosiloxane/poly(meth)alkylacrylate/rigid shell is70-90/5-15/5-15, C) 2 to 20 percent phosphorous-containing flameretarding compound, D) 0.1 to 2 percent fluorinated polyolefin and E)0.1 to 15 percent boron compound said percent, all occurrences beingrelative to the total weight of A), B), C), D), and E), the compositioncharacterized in that it contains no polyalkylene terephthalate.
 2. Thecomposition according to claim 1, wherein said A) is present in anamount of 65 to 90 percent, B) is present in an amount of 3 to 12percent, C) is present in an amount of 5 to 15 percent, D) is present inan amount of 0.2 to 1 percent and said E) is present in an amount of 1to 7 percent.
 3. The composition according to claim 1, wherein said A)is a homopolycarbonate based on bisphenol A.
 4. The composition of claim1 wherein said weight ratio is 75-85/7-12/7-12.
 5. The composition ofclaim 1 wherein said weight ratio is 80/10/10.
 6. The composition ofclaim 1 wherein the rubber core is in particulate form having medianparticle she of 0.05 to 5 micron.
 7. The composition of claim 1, whereinsaid C) conforms to formula (IV)

wherein R¹, R², R³ and R⁴ each independently of the others representsC₁₋₈alkyl, or C₅-₆-cycloalkyl, C₆-₂₀-aryl or C₇₋₁₂-aralkyl eachoptionally substituted by alkyl, n independently of each other is 0 or1, q denotes 0.5 to 30, and X is a mono- or poly-nuclear aromaticradical having 6 to 30 carbon atoms, or a linear or branched aliphaticradical having 2 to 30 carbon atoms, which may be OH-substituted and maycontain up to 8 ether bonds.
 8. The composition according to claim 1further containing at least one member selected from the groupconsisting of styrenic copolymer, lubricant, mold-release agent,nucleating agent, antistatic, thermal stabilizer, hydrolyticalstabilizer, light stabilizer, colorant, pigment, filler, reinforcingagent, flameproofing agent other than component C), and flameproofingsynergist.
 9. The composition of claim 1 wherein said boron compound iszinc borate.